1. Field of the Invention
The present invention generally relates to a heat sink for removing heat from an electronic device, such as a central processing unit of a computer, and in particular, to a composite heat sink comprising an aluminum-extruded base on which a folded fin made by repeatedly folding a thin conductive plate is fixed.
2. The Prior Art
Heat sinks are used to remove heat from an electronic device, such as a central processing unit. There are two general types of heat sinks available on the market, respectively shown in FIGS. 3A, 3B and FIG. 4.
In FIGS. 3A and 3B, an aluminum-extruded heat sink is shown. A heat sink 100 is made by first performing an aluminum extruding process on a structure having a base 102 to form a plurality of fins 104 extending therefrom and defining air passages 106 having a depth of h1 therebetween as shown in FIG. 3A. The heat sink 100 is further machined by sawing the air passages 106 to a depth h2, as shown in FIG. 3B, which is greater than the original depth h1 for increasing the total surface area of the heat sink 100. The sawing operation is time- and labor-consuming. Furthermore, waste is generated during the sawing operation which, unless properly removed and cleaned, obstructs air flow through the passages 106 thereby reducing the heat removal rate of the heat sink 100.
In FIG. 4, a folded fin heat sink 200 is shown. The folded fin 200 is made by repeatedly folding a thin conductive plate to form a number of side walls 202 connected by alternately arranged top and bottom walls 205, 204. A plurality of air passageways 206 are defined between adjacent side walls 202 for air to flow therethrough. The bottom walls 204 are positioned on and attached to a top face 208 of an electronic device 210 from which heat is to be removed. The attachment of the folded fin 200 to the electronic device 210 is usually done by means of an adhesive. Gaps or air voids are usually present between the bottom walls 204 and the electronic device 210 thereby reducing the heat removal rate. Furthermore, the attachment of the folded fin 200 to the electronic device 210 by means of adhesive is unreliable and the folded fin 200 may become easily detached from the electronic device 210.
It is thus desirable to have a heat sink, which does not exhibit the disadvantages associated with conventional heat sinks.